Professional brewers know that dissolved oxygen (DO) is an important measurement in beer. There are times when we want it present, and there are times where its existence can ruin a batch—or simply lead to beer on the shelf that nobody wants to drink.
Successful production teams are often enthusiastic about their DO meters, dialing in their processes to get the lowest possible score going into the package. However, DO meters can be expensive, and that doesn’t include the recurring maintenance costs to ensure continued accuracy. If your brewery can’t justify the cost—or even if it can—there is another way to methodically and effectively improve your beer’s shelf life.
It starts with taking advantage of your senses.
Here, I discuss how to begin improving shelf life by first getting a handle on how well your beer is keeping—by tracking its aging from one week to many months after the package date. But first, let’s briefly review why DO matters.
Be a Librarian
DO is the frenemy of brewers everywhere: It’s helpful early in fermentation to kickstart yeast health and growth, but after fermentation it becomes beer’s nemesis.
The presence of DO, especially in the package, has long-term impacts that deteriorate beer’s quality. Oxygen reacts with lipids in the beer, causing reactions that lead to off-flavors and instability. The lower the DO going into that package, the fresher that beer will taste for longer.
A DO meter is a straightforward way to measure that quantity of oxygen. However, if you don’t have a meter—or even if you do—building a shelf-life library can give you some valuable insights.
All you need to start a shelf-life library are some full cans from your packaging runs and a place to keep them. Ideally, you want two cans each from the beginning, middle, and end of the packaging run. If you have the volume and space, more cans are even better—that lets you test more cans over a longer period of time and potentially pull cans in the event of a customer complaint.
If possible, you should store cans at room temperature or warmer. Storing at warmer temperatures will let you simulate the conditions your beer experiences in shops or bars where your beer isn’t always stored properly. When you finally taste the cans, you’ll be able to determine whether oxygen had a major impact on the sensory.
The Nose Knows
So, what are these sensory cues? The main off-flavor associated with DO is papery or wet carboard, which is caused by trans-2-nonenal. All beer styles will give off a papery flavor, even if hops or malt dominate the recipe. Trans-2-nonenal provides an increase in astringency and dryness to the finish of the beer, and this can be off-putting in high levels.
The presence of wet-cardboard off-flavors in IPAs also tends to be accompanied by an increase in malt flavors. The hop flavors and aromas dissipate more quickly, leaving a more malt-forward beverage over the course of its shelf life.
Finally, aging also can lead to the production of acetaldehyde (green apple/cider). Ethanol reacts to form aldehydes, and acetaldehyde can be detected in lighter beer styles as they age.
If you don’t have the space for the library or need to get results faster, force-aging beers in an incubator can do the trick. Storing cans in an incubator set to around 100°F (38°C) for one week will simulate three months on the shelf. At that temperature, oxidation reactions speed up, and you’ll be able to detect oxygen-related off-flavors much more quickly than if they were stored cold.
After that week, a tasting sample should indicate whether the level of oxygen present in your beer is going to negatively impact the shelf life. In addition, bacterial infections such as those caused by Lactobacillus and Pediococcus can grow faster at these temperatures. So, if an infection is present and was undetected during transfer or packaging, force-aging the beer can bring sour notes and other off-flavors to the forefront.
If you want to test your sensory panel to see whether they can detect off-flavors related to shelf life, triangle tests are a reliable and unbiased method. (See “Brewing Quality: How to Start Up Your Sensory Panel,” brewingindustryguide.com.) A triangle test involves evaluating three samples, two of which are the same while the third is different.
Having panel members attempt to conclude whether there’s a difference among the samples can help you to determine whether any such difference is perceptible. If the participants fail to detect a difference, then you might conclude that the presence of DO and DO-related off-flavors isn’t necessarily enough to make an impact on the consumer’s experience, either.
Pulling the Trigger
Once your brewery is ready to invest in a DO meter, there are plenty of options. Depending on the brand and features, you can expect to pay anywhere from $10,000 to $20,000 for a unit that can read brite tanks and cans.
That cost doesn’t include regular service by an experienced technician—something that should be done at least once a year. You’ll also want to perform cleanings and calibrations on your own device between services. As you track your DO numbers to see whether your values are drifting or not making sense, you don’t want the cause to be a neglected meter.
If you have a shelf-life library in place before purchasing a DO meter, you’ll be able to use the two methods together to make even better, more informed decisions about the shelf life of your beer.
DO meters are an important piece of equipment for breweries as they grow and develop. However, it’s important to implement other methods before you have a DO meter in place. Building a shelf-life library is something that can provide insights into your beer quality for years to come. Plus, you’ll be able to use the methods outlined above to train your senses, and those of your team, to get the best possible idea of how your beer tastes over time.